Problem: In very large aircraft applications, conventional four wheel per post (shock strut) installations require greater stowage volume and may be heavier than desirable due to the fact that a great number of posts are needed together with their supporting structure. Conversely, for a given number of tires, if fewer posts are used, the individual shock strut sizes (diameter and length) must be increased because of higher loads per post and hence require a wider wheel base and usually a longer than desirable wheel well.
Attempts to develop an eight wheel bogie stem from development of a six-wheel bogie (see FIG. 1) with one shock strut mounted on the center axle pivot. However, an eight wheel bogie geometry with a single shock absorber does not permit convenient mounting of the shock strut on one of the axles and requires a separate pivot, otherwise asymmetric loading of the tires would be the result. Studies indicate that a separate pivot results in a weight penalty. Furthermore, evaluation of a single shock strut on eight wheels for application to large aircraft results in a very large shock absorber which current technology may find difficult to build. And finally, the physical size of this arrangement results in poor kinematic retraction which requires the same if not more stowage volume and will typically expose more frontal area to the effects of aerodynamic drag (noise and loads) than the separate four wheel installations which it is supposed to replace. Attempts to reduce the shock strut size and take advantage of the weight saving pivot/axle feature by using twin shock struts failed because the struts were fixed rigid to each other and the resulting kinematic action prevented a simple means of incorporating truck pitch attitude control done by a separate external actuator/damper as shown in FIG. 1.